Light source device and display device

ABSTRACT

Disclosed is a light source device that includes a substrate; a light source portion supported on the substrate and producing a light; a container supported on the light source portion and containing quantum dots excited by the light; and a thermal conductor connecting the container with the substrate.

The present application claims the priority benefit of Japanese PatentApplication No. 2016-170604 filed in Japan on Sep. 1, 2016, which ishereby incorporated by reference in its entirety for all purposes as iffully set forth herein.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a light source device and a displaydevice.

Discussion of the Background Art

Recently, to provide a liquid crystal display device that can display animage with good color reproduction, a research of a technology thatraises a color purity of a light incident on a liquid crystal displayelement has been required. For example, a technology using a quantum dothas been developed. The quantum dot is a fluorescent substance, and whenan excitation light is incident from a light source such as a lightemitting diode (LED), the quantum dot produces a light of a wavelengthlonger than a wavelength of the excitation light. By changing a type anda diameter of the quantum dot, a wavelength of a light produced by thequantum dot can be adjusted. For example, the quantum dot is configuredsuch that it uses a blue light as an excitation light from an LED andproduces a green light and a red light, which are narrow in full widthat half maximum, when the blue light is incident. Accordingly, by usingthe quantum dot, a light source, of high efficiency, which is capable ofproducing a light of a narrow wavelength region corresponding to threeprimary colors of light can be realized.

The quantum dot is prone to a deterioration when being exposed to water,oxygen and heat. A technology described in Japanese Patent ApplicationPublication No. 2016-76634 (referred to herein below as patentliterature 1) seals quantum dots, dispersed in a resin or organicsolvent, inside a container (or vessel) having a barrier property towater and oxygen. By this configuration, a deterioration of a lightsource device including the quantum dots is suppressed and reliabilitycan be improved.

The container sealing the quantum dots is prone to accumulate heatproduced by a non-radiative deactivation or the like. Accordingly, aquantum dot deterioration caused by the accumulated heat at thecontainer may happen. However, the technology in the patent literature 1is capable of suppressing a deterioration by water and oxygen but doesnot consider a deterioration by a heat.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a light source deviceand a display device that can suppress a quantum dot deterioration by aheat.

Additional features and advantages of the disclosure will be set forthin the description which follows, and in part will be apparent from thedescription, or may be learned by practice of the disclosure. Theadvantages of the disclosure will be realized and attained by thestructure particularly pointed out in the written description and claimsas well as the appended drawings.

To achieve these and other advantages, and in accordance with thepurpose of the present invention, as embodied and broadly describedherein, a light source device includes a substrate; a light sourceportion supported on the substrate and producing a light; a containersupported on the light source portion and containing quantum dotsexcited by the light; and a thermal conductor connecting the containerwith the substrate.

In another aspect, a display device includes the above light sourcedevice and a liquid crystal panel supplied with a light from the lightsource device.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate embodiments of the disclosure andtogether with the description serve to explain the principles of thedisclosure. In the drawings:

FIG. 1 is a front view illustrating a display device according to afirst embodiment of the present invention;

FIG. 2 is a cross-sectional view illustrating the display deviceaccording to the first embodiment of the present invention;

FIG. 3 is a cross-sectional view illustrating a quantum dot structureaccording to the first embodiment of the present invention; and

FIG. 4 is a cross-sectional view illustrating the display deviceaccording to a second embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings. The same or like referencenumbers may be used throughout the drawings to refer to the same or likeparts.

First Embodiment

FIG. 1 is a front view illustrating a display device according to afirst embodiment of the present invention. All the components of thedisplay device according to all embodiments of the present invention areoperatively coupled and configured.

Referring to FIG. 1, the display device 10 includes a liquid crystalpanel 20, light source devices 100 arranged over a rear surface of theliquid crystal panel 20, and a frame 30 supporting the liquid crystalpanel 20 and the light source devices 100. In FIG. 1, it is shown thatthe light source devices 100 at the rear of the liquid crystal panel 20are transmitted and seen through liquid crystal panel 20 for the sake ofvisibility. A number and a size of each of portions included in thedisplay device 10 does not consider real components, and may be designedappropriately according to a real installation method.

The light source devices 100 serve as a direct type backlight unit, andradiate a light to the liquid crystal panel 20 from a rear side of theliquid crystal panel 20. A detailed configuration of the light sourcedevices 100 is explained below with reference to FIGS. 2 and 3. Theliquid crystal panel 20 may include known components that include aliquid crystal layer, a polarizing plate, a color filter, an electriccircuit such as a thin film transistor (TFT) and so on. The liquidcrystal panel 20 controls tranmissivity of light, from the light sourcedevices 100, for each pixel using the electric circuit of each pixel,and display a desired image. The frame 30 is formed using a resin, metalor so on, and supports the liquid crystal panel 20 and the light sourcedevices 100. Electric wirings to the liquid crystal panel 20 and thelight source devices 100 are installed in the frame 30. In thisembodiment, the direct type backlight unit is described as a backlightunit by way of example, but an edge type backlight unit may be used.

FIG. 2 is a cross-sectional view, along a line A-A of FIG. 1, of thedisplay device according to the first embodiment of the presentinvention. The light source device 100 includes a light source portion120 producing a light of a predetermined wavelength and a quantum dotstructure 110 converting a wavelength of a light from the light sourceportion 120.

The light source portion 120 includes a light emitting element 121, asubstrate 122 and a frame 123. The light emitting element 121 produces alight of a predetermined wavelength and radiates the light to the liquidcrystal panel 20. The light emitting element 121 is electricallyconnected to an electric wiring, and produces a light using a powerapplied through the electric wiring. A wavelength of the light producedby the light emitting element 121 is, for example, within a wavelengthregion of a blue light (e.g., about 380 nm˜500 nm) or a wavelengthregion of a ultraviolet (UV) light (e.g., about 10 nm˜380 nm). The lightemitting element 121 may use a light emitting diode (LED), an organiclight emitting diode (OLED) or the like. As the light from the lightemitting element 121 is incident, as an excitation light, on the quantumdot structure 110, and the light source device 100 can produce a lightof a narrow wavelength region corresponding to three primary colors oflight.

The frame 123 has a concave shape, and includes a bottom wall 123 a anda side wall 123 b surrounding the bottom wall 123 a. The light emittingelement 121 is supported on the bottom wall 123 a, and the quantum dotstructure 110 is supported on the side wall 123 b, an inside regionenclosed by the bottom wall 123 a and the side wall 123 b is formedbetween the quantum dot structure 110 and the light emitting element121, and a light from the light emitting element 121 to the quantum dotstructure 110 passes through the inside region. To improve a heatradiation property, the bottom wall 123 a and the side wall 123 b of theframe 123 is formed using a thermal conductor such as a high thermallyconductive resin. The high thermally conductive resin may be, forexample, a mixture of a thermally conductive filler, such as an organicparticle, with a resin, such as carbonate or nylon. Alternatively, thethermal conductor may use other material, such as metal orsemiconductor, of a high thermal conductivity.

The substrate 122 extends in parallel with a surface of the liquidcrystal panel 20, and supports the light emitting elements 121 and theframes 123. In this embodiment, a predetermined number of light emittingelements 121 and frames 123 are arranged in a lattice manner and at anequidistant interval from each other, on the substrate 122. A number ofand an arrangement of the light emitting elements 121 and frames 123 maybe set appropriately according to a configuration of the display device10. The substrate 122 may be formed using a resin, metal, semiconductoror the like.

The quantum dot structure 110 is located between the rear surface of theliquid crystal panel 20 and the light source portion 120, and isinterposed on a path of a light from the light source portion 120 to therear surface of the liquid crystal panel 20. The light from the lightsource portion 120 radiates to the rear surface of the liquid crystalpanel 20 through the quantum dot structure 110. FIG. 3 is a detailedcross-sectional view, along a line A-A of FIG. 1, of the quantum dotstructure according to the first embodiment of the present invention.The quantum dot structure 110 includes an airtight container (orairtight vessel), and quantum dots 112 and a dispersion medium 113contained in the airtight container 111. The dispersion medium 113 is amedium in a liquid or solid phase to uniformly disperse the quantum dots112 and is formed using a material, such as a resin or the like,transmitting a light of at least a visible light wavelength region(e.g., about 380 nm˜780 nm).

The airtight container 111 has a container that has an inside regionisolated from an outside space, and is formed using a material, such asa resin, glass or the like, transmitting a light of at least a visiblelight wavelength region. To suppress a deterioration of the quantum dot112 by water and oxygen, it is preferable that the airtight container111 is formed using a material having a barrier property to water andoxygen.

In this embodiment, the airtight container 111 is configured by a glasscell that is formed using a glass having a high barrier property towater and oxygen. In detail, the airtight container 111 has a structure,a quadrangular prism shape, that a bottom wall 111 a and a top wall (orceiling wall) 111 b, which are glass rectangular plates parallel witheach other, face each other at a predetermined interval with a side wall111 c interposed therebetween. The light from the light source portion120 is incident perpendicularly to the bottom wall 111 a. The airtightcontainer 111 is not limited to the structure described by way ofexample in this embodiment but may use a known structure (e.g., seeJapanese Patent Application Publication No. 2015-233057, also referredto herein as patent literature 2). A shape of the airtight container 111may be, for example, other shape such as a cylindrical shape. At least apart of a side wall of the airtight container 111 may have a curvedshape rather than a plan shape.

The quantum dot 112 (which may be referred to as a colloidal quantumdot) is a nano-scale material that has an optical property according toa quantum mechanics, and is a minute semiconductor particle that has adiameter of about 1 nm˜100 nm, preferably 1 nm˜50 nm, more preferably 1nm˜20 nm. The quantum dot 112 absorbs a photon that has an energygreater than a band gap (i.e., an energy difference between a valanceband and a conduction band), and emits a light of a wavelength accordingto its diameter. Accordingly, the quantum dot 112 has a property ofabsorbing a light of a predetermined wavelength or less and can producea light of a predetermined wavelength by adjusting the diameter. In thisembodiment, the quantum dot 112 has a spherical shape by way of example,but it may have other shape.

The quantum dot 112 includes at least one semiconductor material. As thesemiconductor material, a IV group atom, II-VI group compound, II-Vcompound, III-VI compound, III-V compound, IV-VI compound, groupcompound, II-IV-VI compound, II-IV-V compound or the like may be used.In detail, as the semiconductor material of the quantum dot 112, ZnO,ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaSe,GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb,TiN, TiP, TiAs, TiISb, PbO, PbS, PbSe, PbTe, Ge, Si or the like may beused. However, the quantum dot 112 is not limited to the above material,but may use other material sufficient to achieve the ability of thequantum dot 112.

When a light produced by the light source portion 120 is a blue light, afirst quantum dot 112, which has a light-emission center wavelength at awavelength region of a green light (e.g., 510 nm˜610 nm, preferably 520nm˜580 nm), and a second quantum dot 112, which has a light-emissioncenter wavelength at a wavelength region of a red light (e.g., 600nm˜700 nm, preferably 610 nm˜680 nm), are combined and used. In otherwords, the blue light from the light source portion 120 functions as anexcitation light for the quantum dot 112 and also functions as a visiblelight emitted from the light source device 100. In this embodiment, alight source having a light-emission spectrum with 3 maxima of red,green and blue colors is described, but combination of light-emissioncenter wavelengths and quantum dots is not limited and other combinationmay be used.

When a light produced by the light source portion 120 is a UV light, afirst quantum dot 112 having a light-emission center wavelength at awavelength region of a green light, a second quantum dot 112 having alight-emission center wavelength at a wavelength region of a red light,and a third quantum dot 112 having a light-emission center wavelength ata wavelength region of a blue light are combined and used. In otherwords, the UV light from the light source portion 120 functions as anexcitation light for the quantum dot 112.

The quantum dot 112 may has a core-shell type structure that has a coreincluding at least one semiconductor material, and a shell including atleast one semiconductor material.

In detail, a quantum dot 112 using CdSe as a core and CdZnS as a shell,a quantum dot 112 using CdZnSe as a core and CdZnS as a shell, and aquantum dot 112 using CdS as a core and CdZnS as a shell may be used.

Referring back to FIG. 2, means that realize an effective heat radiationin the light source device 100 according to this embodiment areexplained. To achieve a heat radiation from the quantum dot structure110, the light source device 100 includes a high thermally conductivecladding member 130 covering around the side wall 111 c of the quantumdot structure 110, and a high thermally conductive filler 140 fillingthe inside region of the frame 123 of the light source portion 120. Eachof the high thermally conductive cladding member 130 and the highthermally conductive filler 140 thermally connects the quantum dotstructure 110 with the substrate 122 of the light source portion 120,and transfers heat from the quantum dot structure 110 to the substrate122.

In detail, the high thermally conductive cladding member 130 connectsthe side wall 111 c with the surface of the substrate 122. To promote aheat transfer from the quantum dot structure 110 to the high thermallyconductive cladding member 130, the high thermally conductive claddingmember 130 contacts a ⅓ or greater, in a height direction, of the sidewall 111 c, preferably a half or greater, in a height direction, of theside wall 111 c, and more preferably all, in a height direction, of theside wall 111 c. The high thermally conductive cladding member 130contacts at least a part, in a perimeter direction, of the side wall 111c, and preferably all, in a perimeter direction, of the side wall 111 c.To increase an amount of heat radiation from the high thermallyconductive cladding member 130 itself, it is preferable that the highthermally conductive cladding member 130 has an unevenness (e.g.,concavo-convex pattern) at a surface thereof to increase a surface area.

In this embodiment, the high thermally conductive cladding member 130may be formed by coating a high thermally conductive paste, which isobtained by making a thermal conductor into a paste phase, on surfacesof the side wall 111 of the quantum dot structure 110, the side wall 123b of the light source portion 120, and the substrate 122 such that thepaste continuously contacts the surfaces of the side wall 111 of thequantum dot structure 110, the side wall 123 b of the light sourceportion 120, and the substrate 122. The thermal conductor of the highthermally conductive cladding member 130 may use a metal, semiconductor,or above-described high thermally conductive resin. By thisconfiguration, the heat produced at the quantum dot structure 110 istransferred from the side wall 111 c of the quantum dot structure 110 tothe substrate 122 via the high thermally conductive cladding member 130,and then is emitted from the substrate 122.

The high thermally conductive filler 140 connects the bottom wall 111 aof the quantum dot structure 110 with the bottom wall 123 a of the lightsource portion 120. To suppress a loss of light from the light emittingelement 121, it is preferable that the high thermally conductive filler140 fully fills the inside region enclosed by the bottom wall 123 a andthe side wall 123 b of the light source portion 120 and there is nospace on a light path from the light emitting element 121 to the quantumdot structure 110.

In this embodiment, the high thermally conductive filler 140 is formedby filling the inside region, enclosed by the bottom wall 123 a and theside wall 123 b of the light source portion 120, with a thermalconductor. The thermal conductor of the high thermally conductive filler140 may use an inorganic material, which transmits a wavelength regionof a light from the light emitting element 121, a high thermallyconductive resin and so on. Since the frame 122 of the light sourceportion 120 usually has a heat transfer amount greater than anatmosphere, a heat from the high thermally conductive filler 140 iseasily conducted to the substrate 122. By this configuration, the heatproduced at the quantum dot structure 110 is transferred from the bottomwall 111 a of the quantum dot structure 110 to the substrate 122 via thehigh thermally conductive filler 140 and the frame 123 of the lightsource portion 120, and then is emitted from the substrate 122.

Further, a heat sink 150, which is a heat radiation portion from thesubstrate 122, is installed at the substrate 122. The heat sink 150 hasuneven patterns at a surface thereof and is a member to increase a heatradiation property. To increase an installation area of the heat sink150, it is preferable that the heat sink 150 is installed at a side,opposite to the quantum dot structure 110, of the substrate 122. A heat,which is conducted from the quantum dot structure 110 to the substrate122 through the high thermally conductive cladding member 130 and thehigh thermally conductive filler 140, is further effectively emittedfrom the heat sink 150 of the substrate 122. Besides the heat sink 150,the heat radiation portion from the substrate 122 may use otherstructure, for example, a heat radiation paint coated on the surface ofthe substrate 122. Further, by forming uneven patterns at the surface ofthe, the substrate 122 itself may function as the heat radiationportion.

Since the substrate 122 of the light source portion 120 has a largearea, the substrate 122 has a heat radiation property greater than theairtight container 111 of the quantum dot structure 110. The heatradiation property of the substrate 122 further rises because of theheat sink 150. Accordingly, according to the light source device 100 ofthe embodiment, since the heat produced at the quantum dot structure 110is transferred to the substrate 122 using the high thermally conductivecladding member 130 and the high thermally conductive filler 140, theheat radiation amount from the quantum dot structure 110 can increaseand a deterioration of the quantum dot 112 by a heat can be suppressed.

In this embodiment, by both of the high thermally conductive claddingmember 130 and the high thermally conductive filler 140, the quantum dotstructure 110 and the substrate 122 are thermally connected. However,even when employing one of the high thermally conductive cladding member130 and the high thermally conductive filler 140, the effect of thisembodiment can be also achieved.

Example of Present Invention

An acceleration test for an example of this embodiment that is the lightsource device 100 described above is conducted. Further, an accelerationtest for a first comparative example that omits the high thermallyconductive cladding member 130 and the heat sink 150 from the lightsource device 100, and an acceleration test for a second comparativeexample that omits the high thermally conductive cladding member 130from the light source device 100 are conducted. A condition for theacceleration tests is that the light emitting diode 100 is fabricatedusing an LED having a center wavelength of 450 nm as the light emittingelement 121, and the LED is turned on at an environmental temperature of85 degrees Celsius. A total luminous flux for a state before an LEDturn-on and a total luminous flux for a state after 70 hours aremeasured, and a luminous flux maintenance factor between the states iscalculated. The luminous flux maintenance factor is expressed as arelative value with respect to the first comparative example of 100%,and as the higher maintenance factor is considered better because adeterioration of the quantum dot becomes more suppressed. Further, avisual inspection for each of the example of this embodiment, the firstcomparative example, and the second comparative example is conducted.The visual inspection is to evaluate how much a color of the quantum dot112 and the dispersion medium 113 becomes black by a deterioration. Themeasuring results are shown in Table 1.

TABLE 1 Luminous flux maintenance factor (relative value with Visualrespect to the first inspec- comparative example) tion Example of thisembodiment 133 Very (with high thermally conductive good cladding memberand heat sink) 1^(st) comparative example 100 Bad (without highthermally conductive cladding member and heat sink) 2^(nd) comparativeexample 108 Good (without high thermally conductive cladding member andwith heat sink)

As shown in Table 1, the example of this embodiment has the luminousflux maintenance factor improved significantly compared with the firstcomparative example without the high thermally conductive claddingmember 130 and the heat sink 150. Further, the example of thisembodiment has the luminous flux maintenance factor improved comparedwith the second comparative example with the heat sink 150 installed onthe rear surface of the substrate 122. Regarding the deteriorationevaluation of the quantum dot by the visual inspection, the example ofthis embodiment is better than the first and second comparativeexamples. Therefore, it is established that installing the highthermally conductive cladding member 130, which connects the quantum dotstructure 110 and the substrate 122, is effective to improvements ofheat radiation property and reliability of the quantum dot structure110.

Second Embodiment

FIG. 4 is a cross-sectional view, along a line A-A of FIG. 1, of adisplay device according to a second embodiment of the presentinvention. A configuration of a quantum dot structure 110 of thisembodiment is different from that of the first embodiment. Except forthe configuration of the quantum dot structure 110, this embodiment issubstantially identical to the second embodiment.

In the display device 10 of this embodiment, the high thermallyconductive cladding member 130 is omitted, and instead of this, a heatsink 160 as a heat radiation portion from the quantum dot structure 110is installed on a surface of the side wall 111 c of the quantum dotstructure 110. The heat sink 160 has uneven patterns at a surfacethereof and is thus a member raising a heat radiation property. Further,by installing the uneven patterns on the surface of the side wall 111 cof the quantum dot structure 110, the side wall 111 c itself may serveas a heat radiation portion. A means to serve the side wall 111 c itselfas a heat radiation portion is not limited to the uneven patters at thesurface, but may use other structure, for example, a heat radiationpaint coated on the surface.

As a heat radiation portion from the quantum dot structure 110, insteadof the heat sink 160, an air-cooling or water-cooling device may beinstalled, which performs a forced air cooling by circulating a gas orliquid in a circulation pipe installed an inside or surface of thebottom wall 111 a, top wall 111 b or side wall 111 c of the airtightcontainer 111.

According to the display device 10 of this embodiment, since the heatproduced at the quantum dot structure 110 is transferred to thesubstrate 122 using the high thermally conductive filler 140 and is alsoemitted from the heat sink 160 installed at the quantum dot structure110, the heat radiation amount from the quantum dot structure 110 canincrease and a deterioration of the quantum dot 112 by a heat can besuppressed.

With a combination of the first and second embodiments, both of the highthermally conductive cladding member 130 and the heat sink 160 may beinstalled at the side wall 111 c of the quantum dot structure 110.Accordingly, the heat radiation amount from the quantum dot structure110 can further increase.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in a display device of thepresent invention without departing from the sprit or scope of thedisclosure. Thus, it is intended that the present invention covers themodifications and variations of this disclosure provided they comewithin the scope of the appended claims and their equivalents.

What is claimed is:
 1. A light source device, comprising: a substrate; a light source portion supported on the substrate and producing a light; a container supported on the light source portion and containing quantum dots excited by the light; and a thermal conductor connecting the container with the substrate, wherein the container includes a first bottom wall on which the light is incident, and a first side wall surrounding the first bottom wall, and wherein the thermal conductor connects the first side wall of the container with the substrate.
 2. The light source device of claim 1, wherein the light source portion includes a light emitting element producing the light, a second bottom wall supporting the light emitting element, and a second side wall surrounding the second bottom wall, and wherein the thermal conductor is continuously installed to contact a surface of the first side wall, a surface of the second side wall and a surface of the substrate.
 3. The light source device of claim 1, wherein the thermal conductor includes a high thermally conductive resin, a high thermally conductive paste, a metal or a semiconductor.
 4. The light source device of claim 1, wherein a heat radiation portion is installed at a surface, opposite to the container, of the substrate.
 5. A display device, comprising: the light source device of claim 1; and a liquid crystal panel placed at a location to which the light from the light source device is radiated.
 6. A light source device, comprising: a substrate; a light source portion supported on the substrate and producing a light; a container supported on the light source portion and containing quantum dots excited by the light; and a thermal conductor connecting the container with the substrate, wherein the light source portion includes a light emitting element producing the light, a second bottom wall supporting the light emitting element, and a second side wall surrounding the second bottom wall, and wherein the thermal conductor connects the container and the second bottom wall.
 7. The light source device of claim 6, wherein the thermal conductor fills a region enclosed by the container, the second bottom wall and the second side wall.
 8. The light source device of claim 6, wherein the thermal conductor transmits the light.
 9. The light source device of claim 6, wherein the thermal conductor includes a high thermally conductive resin.
 10. A display device, comprising: the light source device of claim 6; and a liquid crystal panel placed at a location to which the light from the light source device is radiated.
 11. A light source device, comprising: a substrate; a light source portion supported on the substrate and producing a light; a container supported on the light source portion and containing quantum dots excited by the light; and a thermal conductor connecting the container with the substrate, wherein the container includes a first bottom wall on which the light is incident, and a first side wall surrounding the first bottom wall, and wherein a heat radiation portion is installed at the first side wall.
 12. A display device, comprising: the light source device of claim 11; and a liquid crystal panel placed at a location to which the light from the light source device is radiated. 